Mobile information terminals having a touch sensitive screen as a user interface have been coming into use in recent years. The user can intuitively operate the mobile information terminal with a touch sensitive screen by touching the screen with a finger or by sliding the finger on the screen. Many recent mobile information terminals incorporate an accelerometer, and those mobile information terminals can automatically switch the display orientation of the display screen in accordance of the direction of gravitational force sensed by the accelerometer. This allows the user to use the mobile information terminal in a variety of gripping states and operation states according to the circumstances. For example, the user may grip the mobile information terminal in the right hand and operate the terminal with the right fingers alone (right thumb mainly), may grip the mobile information terminal in the left hand and operate the terminal with the left fingers alone (left thumb mainly), may grip the mobile information terminal in the right hand and operate the terminal with the left fingers alone (left index finger mainly), and may grip the mobile information terminal in the left hand and operate the terminal with the right fingers alone (right index finger mainly). Moreover, the user may not grip the mobile information terminal but may place it on a stand and operate it with right fingers or left fingers, and may also grip the mobile information terminal in both hands and operate it with fingers of both hands (both thumbs mainly), for example.
Although the gripping states and operation states of the mobile information terminal vary as described above, conventional mobile information terminals cannot perform screen display suited to each gripping state and each operation state. For example, if the user grips the terminal in the right (left) hand and attempts to operate the touch sensitive screen with the right (left) thumb (this operation method will be referred to as one-handed operation), some areas of the touch sensitive screen, such as the top right corner, the bottom left corner, the top left corner, and the bottom right corner, become difficult to reach for the right (left) thumb. If an icon or link is displayed in those areas, it has been difficult for the user to touch the icon or link displayed in those areas while performing one-handed operation. For example, when the user of the mobile information terminal is going to operate the mobile information terminal, while standing in a moving train, the user would hold on to a strap or a rail with one hand so that he or she will not stagger and would perform one-handed operation of the mobile information terminal with the other hand.
If an icon or link the user wants to reach is displayed in an area that is difficult to reach for the right (left) thumb on the touch sensitive screen, the user should give up the operation until the next time the train stops and operate the mobile information terminal with both hands when the train has stopped, or should release the strap or rail temporarily in the moving train and operate the mobile information terminal with both hands temporarily. If the train jolts while the user is not holding on to the strap or rail, the user may fall down. If this occurs in a crowded train, the user could bump into another passenger or could step on the foot of another passenger. The same inconvenience will occur when the user attempts to operate the mobile information terminal with one hand while carrying in the other hand a load that cannot be carried on his or her back. The user has to lower the load onto the ground and then operate the mobile information terminal.
A portable terminal in Patent Literature 1 utilizes a touch sensor (left sensor) disposed in the upper part of the left edge of the housing and a touch sensor (right sensor) disposed in the upper part of the right edge of the housing and solves the problems described above by determining whether the user's current holding state is left-handed operation, right-handed operation, or two-handed operation, using the states of thumbs detected by the left and right sensors and the detected state of the touch sensitive screen. When the detected states of the left sensor, right sensor, and touch sensitive screen are expressed by a circle (detection) or a cross (no detection), if the left and right sensors and the touch sensitive screen make no detection, for example, the state can be expressed as (left sensor, right sensor, touch sensitive screen)=(x, x, x). When the initial state S1 is defined as a state in which the user is neither gripping the portable terminal nor touching the touch sensitive screen, the initial state S1 can be expressed as (x, x, x). When a change from the initial state (x, x, x) to a state (O, x, x) is detected, it is determined that the left thumb is placed on the upper part of the left edge of the housing of the portable terminal, and the state shifts to a left-hand-holding state S2. When a change from the left-hand-holding state S2 (O, x, x) to the state (x, x, x) is detected, it is determined that the thumb is moving to touch the touch sensitive screen, and the state shifts to a prior-to-left-handed-operation state S3. When a change from the prior-to-left-handed-operation state S3 (x, x, x) to a state (x, x, O) is detected, it is determined that the thumb has touched the touch sensitive screen, and the state shifts to a subsequent-to-left-handed-operation state S4. When a change from the left-hand-holding state S2 (O, x, x) to a state (O, x, O) is detected, it is determined that the terminal is held in the left hand and the touch sensitive screen is operated with a right finger, and the state changes to a left-hand-holding right-handed-operation state S5.
The same goes for the right hand. When a change from the initial state (x, x, x) to a state (x, O, x) is detected, it is determined that the right thumb is placed on the upper part of the right edge of the housing of the portable terminal, and the state shifts to a right-hand-holding state S6. When a change from the right-hand-holding state S6 (x, O, x) to a state (x, x, x) is detected, it is determined that the thumb is moving to touch the touch sensitive screen, and the state shifts to a prior-to-right-handed-operation state S7. When a change from the prior-to-right-handed-operation state S7 (x, x, x) to a state (x, x, O) is detected, it is determined that the thumb has touched the touch sensitive screen, and the state shifts to a subsequent-to-right-handed-operation state S8. When a change from the right-hand-holding state S6 (x, O, x) to a state (x, O, O) is detected, it is determined that the terminal is held in the right hand and the touch sensitive screen is operated with a left finger, and the state shifts to a right-hand-holding left-handed-operation state S9. The terminal in Patent Literature 1 determines whether the user's current holding state is left-handed operation, right-handed operation, or two-handed operation, as described above, and re-positions the control buttons on the touch sensitive screen so that they can be reached easily in any holding state.
Patent literature 1: Japanese Patent Application Laid Open No. 2009-169820